I. Field of the Invention
The present invention relates to a paging receiver used in a paging communication system.
II. Description of the Prior Art
Conventional paging receivers frequently adopt a tone generating system wherein a code corresponding to a predetermined identification (ID) number is stored in a memory, a coincidence between a received and decoded code and the code read out from the memory is detected, and an audible tone is produced in response to detection of this coincidence to indicate to a desired receiver-holder that he is being paged. A typical example of the newly developed paging receivers adopting this system is a "RADIO PAGER WITH REDUCED POWER CONSUMPTION" in U.S. Pat. No. 4,323,881 of the same applicant issued Apr. 6, 1982. This pager comprises: a receiver circuit for receiving a carrier wave modulated with a predetermined tone signal as a digit of an ID number given to the pager and demodulating the carrier wave to produce the tone signal; a read-only memory (ROM) for storing codes each associated with a corresponding tone signal constituting a digit of the ID number; a readout circuit for sequentially reading out the codes from the ROM; a hold circuit for holding the codes read out from the ROM; a first decoder for decoding any one of the codes read out from the ROM; a variable band-pass filter responsive to a decoded output from the fist decoder to selectively pass the corresponding tone signal demodulated by the receiver circuit; a tone detector for detecting the modulated tone signal passed through the variable band-pass filter; and a second decoder for decoding an output from the tone detector and causing the readout circuit to read out the code from the ROM. In this pager, the read time of the ROM can be decreased by the readout circuit and the hold circuit, thereby decreasing power consumption of the ROM and hence resulting in an advantage.
However, in the pager or paging receiver of the type described above, when the hold circuit comprising low-power consumption elements such as CMOSs is used to hold the code read out from the ROM, the CMOS tends to be influenced by an induced noise component. Therefore, the readout data from the ROM is altered by a pulsed electrostatic noise component. As a result, the pager having the predetermined ID number cannot be paged. In order to eliminate this problem, the power switch must first be turned off and then be turned on, thus resulting in inconvenience.